I can't get back to the 1950s but I can get back to the early 1960s.
The original Paddington-Birmingham route was via Reading and Oxford, until the shorter High Wycombe route opened to Banbury in 1910.
If you can believe it, there were then no through trains between Reading, Oxford and Birmingham except the Paddington-Oxford-Birkenhead sleeper.
That's not quite true. In 1963 there was an 0655 Paddington-Snow Hill and 1600 Snow Hill-Paddington that ran via Reading. There was also a 1010 Snow Hill-Reading and 1300 Reading-Snow Hill.
The Margate-Wolverhampton and vice versa went via Reading, daily in 1960 but summer Saturdays only by 1963.
There were also 2 key daily cross country trains that called at Reading West, the Pines Express Bournemouth-Manchester and the Bournemouth-York via the Great Central.
In 1963 BR announced London-Birmingham services would be concentrated on the Euston-Rugby-New St route after WCML electrification was completed in 1967.
The WCML electrification and the closure of the Great Central were key changes. From 1967 there was a 1tp2h Paddington-New Street via Reading and Solihull. There were also 3 cross country trains each way to/from Southampton, Bournemouth or Poole, the middle one being the York train diverted from the Great Central.
The next big changes were in the late 1970s following the opening of the National Exhibition Centre and Birmingham International.